<?php

/**
 * @file
 * Field attach API, allowing entities (nodes, users, ...) to be 'fieldable'.
 */

/**
 * Exception thrown by field_attach_validate() on field validation errors.
 */
class FieldValidationException extends FieldException {
	var $errors;

	/**
	 * Constructor for FieldValidationException.
	 *
	 * @param $errors
	 *   An array of field validation errors, keyed by field name and
	 *   delta that contains two keys:
	 *   - 'error': A machine-readable error code string, prefixed by
	 *     the field module name. A field widget may use this code to decide
	 *     how to report the error.
	 *   - 'message': A human-readable error message such as to be
	 *     passed to form_error() for the appropriate form element.
	 */
	function __construct($errors) {
		$this->errors = $errors;
		parent::__construct(t('Field validation errors'));
	}
}

/**
 * @defgroup field_storage Field Storage API
 * @{
 * Implement a storage engine for Field API data.
 *
 * The Field Attach API uses the Field Storage API to perform all "database
 * access". Each Field Storage API hook function defines a primitive database
 * operation such as read, write, or delete. The default field storage module,
 * field_sql_storage.module, uses the local SQL database to implement these
 * operations, but alternative field storage backends can choose to represent
 * the data in SQL differently or use a completely different storage mechanism
 * such as a cloud-based database.
 *
 * Each field defines which storage backend it uses. The Drupal system variable
 * 'field_storage_default' identifies the storage backend used by default.
 *
 * See @link field Field API @endlink for information about the other parts of
 * the Field API.
 */

/**
 * Argument for an update operation.
 *
 * This is used in hook_field_storage_write when updating an
 * existing entity.
 */
define('FIELD_STORAGE_UPDATE', 'update');

/**
 * Argument for an insert operation.
 *
 * This is used in hook_field_storage_write when inserting a new entity.
 */
define('FIELD_STORAGE_INSERT', 'insert');

/**
 * @} End of "defgroup field_storage"
 */

/**
 * @defgroup field_attach Field Attach API
 * @{
 * Operate on Field API data attached to Drupal entities.
 *
 * Field Attach API functions load, store, display, generate Form API
 * structures, and perform a variety of other functions for field data attached
 * to individual entities.
 *
 * Field Attach API functions generally take $entity_type and $entity arguments
 * along with additional function-specific arguments. $entity_type is the type
 * of the fieldable entity, such as 'node' or 'user', and $entity is the entity
 * itself.
 *
 * hook_entity_info() is the central place for entity types to define if and
 * how Field API should operate on their entity objects. Notably, the
 * 'fieldable' property needs to be set to TRUE.
 *
 * The Field Attach API uses the concept of bundles: the set of fields for a
 * given entity is defined on a per-bundle basis. The collection of bundles for
 * an entity type is defined its hook_entity_info() implementation. For
 * instance, node_entity_info() exposes each node type as its own bundle. This
 * means that the set of fields of a node is determined by the node type. The
 * Field API reads the bundle name for a given entity from a particular
 * property of the entity object, and hook_entity_info() defines which property
 * to use. For instance, node_entity_info() specifies:
 * @code $info['entity keys']['bundle'] = 'type'@endcode
 * This indicates that for a particular node object, the bundle name can be
 * found in $node->type. This property can be omitted if the entity type only
 * exposes a single bundle (all entities of this type have the same collection
 * of fields). This is the case for the 'user' entity type.
 *
 * Most Field Attach API functions define a corresponding hook function that
 * allows any module to act on Field Attach operations for any entity after the
 * operation is complete, and access or modify all the field, form, or display
 * data for that entity and operation. For example, field_attach_view() invokes
 * hook_field_attach_view_alter(). These all-module hooks are distinct from
 * those of the Field Types API, such as hook_field_load(), that are only
 * invoked for the module that defines a specific field type.
 *
 * field_attach_load(), field_attach_insert(), and field_attach_update() also
 * define pre-operation hooks, e.g. hook_field_attach_pre_load(). These hooks
 * run before the corresponding Field Storage API and Field Type API
 * operations. They allow modules to define additional storage locations (e.g.
 * denormalizing, mirroring) for field data on a per-field basis. They also
 * allow modules to take over field storage completely by instructing other
 * implementations of the same hook and the Field Storage API itself not to
 * operate on specified fields.
 *
 * The pre-operation hooks do not make the Field Storage API irrelevant. The
 * Field Storage API is essentially the "fallback mechanism" for any fields
 * that aren't being intercepted explicitly by pre-operation hooks.
 *
 * @link field_language Field Language API @endlink provides information about
 * the structure of field objects.
 *
 * See @link field Field API @endlink for information about the other parts of
 * the Field API.
 */

/**
 * Invoke a field hook.
 *
 * @param $op
 *   Possible operations include:
 *   - form
 *   - validate
 *   - presave
 *   - insert
 *   - update
 *   - delete
 *   - delete revision
 *   - view
 *   - prepare translation
 * @param $entity_type
 *   The type of $entity; e.g. 'node' or 'user'.
 * @param $entity
 *   The fully formed $entity_type entity.
 * @param $a
 *   - The $form in the 'form' operation.
 *   - The value of $view_mode in the 'view' operation.
 *   - Otherwise NULL.
 * @param $b
 *   - The $form_state in the 'submit' operation.
 *   - Otherwise NULL.
 * @param $options
 *   An associative array of additional options, with the following keys:
 *  - 'field_name': The name of the field whose operation should be
 *    invoked. By default, the operation is invoked on all the fields
 *    in the entity's bundle. NOTE: This option is not compatible with
 *    the 'deleted' option; the 'field_id' option should be used
 *    instead.
 *  - 'field_id': The id of the field whose operation should be
 *    invoked. By default, the operation is invoked on all the fields
 *    in the entity's' bundles.
 *  - 'default': A boolean value, specifying which implementation of
 *    the operation should be invoked.
 *    - if FALSE (default), the field types implementation of the operation
 *      will be invoked (hook_field_[op])
 *    - If TRUE, the default field implementation of the field operation
 *      will be invoked (field_default_[op])
 *    Internal use only. Do not explicitely set to TRUE, but use
 *    _field_invoke_default() instead.
 *  - 'deleted': If TRUE, the function will operate on deleted fields
 *    as well as non-deleted fields. If unset or FALSE, only
 *    non-deleted fields are operated on.
 *  - 'language': A language code or an array of language codes keyed by field
 *    name. It will be used to narrow down to a single value the available
 *    languages to act on.
 */
function _field_invoke($op, $entity_type, $entity, &$a = NULL, &$b = NULL, $options = array()) {
	// Merge default options.
	$default_options = array(
			'default' => FALSE,
			'deleted' => FALSE,
			'language' => NULL,
	);
	$options += $default_options;

	// Determine the list of instances to iterate on.
	list(, , $bundle) = entity_extract_ids($entity_type, $entity);
	$instances = _field_invoke_get_instances($entity_type, $bundle, $options);

	// Iterate through the instances and collect results.
	$return = array();
	foreach ($instances as $instance) {
		// field_info_field() is not available for deleted fields, so use
		// field_info_field_by_id().
		$field = field_info_field_by_id($instance['field_id']);
		$field_name = $field['field_name'];
		$function = $options['default'] ? 'field_default_' . $op : $field['module'] . '_field_' . $op;
		if (function_exists($function)) {
			// Determine the list of languages to iterate on.
			$available_languages = field_available_languages($entity_type, $field);
			$languages = _field_language_suggestion($available_languages, $options['language'], $field_name);

			foreach ($languages as $langcode) {
				$items = isset($entity->{$field_name}[$langcode]) ? $entity->{$field_name}[$langcode] : array();
				$result = $function($entity_type, $entity, $field, $instance, $langcode, $items, $a, $b);
				if (isset($result)) {
					// For hooks with array results, we merge results together.
					// For hooks with scalar results, we collect results in an array.
					if (is_array($result)) {
						$return = array_merge($return, $result);
					}
					else {
						$return[] = $result;
					}
				}

				// Populate $items back in the field values, but avoid replacing missing
				// fields with an empty array (those are not equivalent on update).
				if ($items !== array() || isset($entity->{$field_name}[$langcode])) {
					$entity->{$field_name}[$langcode] = $items;
				}
			}
		}
	}

	return $return;
}

/**
 * Invoke a field hook across fields on multiple entities.
 *
 * @param $op
 *   Possible operations include:
 *   - load
 *   - prepare_view
 *   For all other operations, use _field_invoke() / field_invoke_default()
 *   instead.
 * @param $entity_type
 *   The type of $entity; e.g. 'node' or 'user'.
 * @param $entities
 *   An array of entities, keyed by entity id.
 * @param $a
 *   - The $age parameter in the 'load' operation.
 *   - Otherwise NULL.
 * @param $b
 *   Currently always NULL.
 * @param $options
 *   An associative array of additional options, with the following keys:
 *  - 'field_name': The name of the field whose operation should be
 *    invoked. By default, the operation is invoked on all the fields
 *    in the entity's bundle. NOTE: This option is not compatible with
 *    the 'deleted' option; the 'field_id' option should be used instead.
 *  - 'field_id': The id of the field whose operation should be
 *    invoked. By default, the operation is invoked on all the fields
 *    in the entity's' bundles.
 *  - 'default': A boolean value, specifying which implementation of
 *    the operation should be invoked.
 *    - if FALSE (default), the field types implementation of the operation
 *      will be invoked (hook_field_[op])
 *    - If TRUE, the default field implementation of the field operation
 *      will be invoked (field_default_[op])
 *    Internal use only. Do not explicitely set to TRUE, but use
 *    _field_invoke_multiple_default() instead.
 *  - 'deleted': If TRUE, the function will operate on deleted fields
 *    as well as non-deleted fields. If unset or FALSE, only
 *    non-deleted fields are operated on.
 *  - 'language': A language code or an array of arrays of language codes keyed
 *    by entity id and field name. It will be used to narrow down to a single
 *    value the available languages to act on.
 *
 * @return
 *   An array of returned values keyed by entity id.
 */
function _field_invoke_multiple($op, $entity_type, $entities, &$a = NULL, &$b = NULL, $options = array()) {
	// Merge default options.
	$default_options = array(
			'default' => FALSE,
			'deleted' => FALSE,
			'language' => NULL,
	);
	$options += $default_options;
	$field_info = field_info_field_by_ids();

	$fields = array();
	$grouped_instances = array();
	$grouped_entities = array();
	$grouped_items = array();
	$return = array();

	// Go through the entities and collect the fields on which the hook should be
	// invoked.
	//
	// We group fields by id, not by name, because this function can operate on
	// deleted fields which may have non-unique names. However, entities can only
	// contain data for a single field for each name, even if that field
	// is deleted, so we reference field data via the
	// $entity->$field_name property.
	foreach ($entities as $entity) {
		// Determine the list of instances to iterate on.
		list($id, $vid, $bundle) = entity_extract_ids($entity_type, $entity);
		$instances = _field_invoke_get_instances($entity_type, $bundle, $options);

		foreach ($instances as $instance) {
			$field_id = $instance['field_id'];
			$field_name = $instance['field_name'];
			$field = $field_info[$field_id];
			$function = $options['default'] ? 'field_default_' . $op : $field['module'] . '_field_' . $op;
			if (function_exists($function)) {
				// Add the field to the list of fields to invoke the hook on.
				if (!isset($fields[$field_id])) {
					$fields[$field_id] = $field;
				}
				// Extract the field values into a separate variable, easily accessed
				// by hook implementations.
				// Unless a language suggestion is provided we iterate on all the
				// available languages.
				$available_languages = field_available_languages($entity_type, $field);
				$language = !empty($options['language'][$id]) ? $options['language'][$id] : $options['language'];
				$languages = _field_language_suggestion($available_languages, $language, $field_name);
				foreach ($languages as $langcode) {
					$grouped_items[$field_id][$langcode][$id] = isset($entity->{$field_name}[$langcode]) ? $entity->{$field_name}[$langcode] : array();
					// Group the instances and entities corresponding to the current
					// field.
					$grouped_instances[$field_id][$langcode][$id] = $instance;
					$grouped_entities[$field_id][$langcode][$id] = $entities[$id];
				}
			}
		}
		// Initialize the return value for each entity.
		$return[$id] = array();
	}

	// For each field, invoke the field hook and collect results.
	foreach ($fields as $field_id => $field) {
		$field_name = $field['field_name'];
		$function = $options['default'] ? 'field_default_' . $op : $field['module'] . '_field_' . $op;
		// Iterate over all the field translations.
		foreach ($grouped_items[$field_id] as $langcode => &$items) {
			$entities = $grouped_entities[$field_id][$langcode];
			$instances = $grouped_instances[$field_id][$langcode];
			$results = $function($entity_type, $entities, $field, $instances, $langcode, $items, $a, $b);
			if (isset($results)) {
				// Collect results by entity.
				// For hooks with array results, we merge results together.
				// For hooks with scalar results, we collect results in an array.
				foreach ($results as $id => $result) {
					if (is_array($result)) {
						$return[$id] = array_merge($return[$id], $result);
					}
					else {
						$return[$id][] = $result;
					}
				}
			}
		}

		// Populate field values back in the entities, but avoid replacing missing
		// fields with an empty array (those are not equivalent on update).
		foreach ($grouped_entities[$field_id] as $langcode => $entities) {
			foreach ($entities as $id => $entity) {
				if ($grouped_items[$field_id][$langcode][$id] !== array() || isset($entity->{$field_name}[$langcode])) {
					$entity->{$field_name}[$langcode] = $grouped_items[$field_id][$langcode][$id];
				}
			}
		}
	}

	return $return;
}

/**
 * Invoke field.module's version of a field hook.
 *
 * This function invokes the field_default_[op]() function.
 * Use _field_invoke() to invoke the field type implementation,
 * hook_field_[op]().
 *
 * @see _field_invoke()
 */
function _field_invoke_default($op, $entity_type, $entity, &$a = NULL, &$b = NULL, $options = array()) {
	$options['default'] = TRUE;
	return _field_invoke($op, $entity_type, $entity, $a, $b, $options);
}

/**
 * Invoke field.module's version of a field hook on multiple entities.
 *
 * This function invokes the field_default_[op]() function.
 * Use _field_invoke_multiple() to invoke the field type implementation,
 * hook_field_[op]().
 *
 * @see _field_invoke_multiple()
 */
function _field_invoke_multiple_default($op, $entity_type, $entities, &$a = NULL, &$b = NULL, $options = array()) {
	$options['default'] = TRUE;
	return _field_invoke_multiple($op, $entity_type, $entities, $a, $b, $options);
}

/**
 * Helper for _field_invoke(): retrieves a list of instances to operate on.
 *
 * @param $entity_type
 *   The entity type.
 * @param $bundle
 *   The bundle name.
 * @param $options
 *   An associative array of options, as provided to _field_invoke(). Only the
 *   following keys are considered :
 *   - deleted
 *   - field_name
 *   - field_id
 *   See _field_invoke() for details.
 *
 * @return
 *   The array of selected instance definitions.
 */
function _field_invoke_get_instances($entity_type, $bundle, $options) {
	if ($options['deleted']) {
		// Deleted fields are not included in field_info_instances(), and need to
		// be fetched from the database with field_read_instances().
		$params = array('entity_type' => $entity_type, 'bundle' => $bundle);
		if (isset($options['field_id'])) {
			// Single-field mode by field id: field_read_instances() does the filtering.
			// Single-field mode by field name is not compatible with the 'deleted'
			// option.
			$params['field_id'] = $options['field_id'];
		}
		$instances = field_read_instances($params, array('include_deleted' => TRUE));
	}
	elseif (isset($options['field_name'])) {
		// Single-field mode by field name: field_info_instance() does the
		// filtering.
		$instances = array(field_info_instance($entity_type, $options['field_name'], $bundle));
	}
	else {
		$instances = field_info_instances($entity_type, $bundle);
		if (isset($options['field_id'])) {
			// Single-field mode by field id: we need to loop on each instance to
			// find the right one.
			foreach ($instances as $instance) {
				if ($instance['field_id'] == $options['field_id']) {
					$instances = array($instance);
					break;
				}
			}
		}
	}

	return $instances;
}

/**
 * Add form elements for all fields for an entity to a form structure.
 *
 * The form elements for the entity's fields are added by reference as direct
 * children in the $form parameter. This parameter can be a full form structure
 * (most common case for entity edit forms), or a sub-element of a larger form.
 *
 * By default, submitted field values appear at the top-level of
 * $form_state['values']. A different location within $form_state['values'] can
 * be specified by setting the '#parents' property on the incoming $form
 * parameter. Because of name clashes, two instances of the same field cannot
 * appear within the same $form element, or within the same '#parents' space.
 *
 * For each call to field_attach_form(), field values are processed by calling
 * field_attach_form_validate() and field_attach_submit() on the same $form
 * element.
 *
 * Sample resulting structure in $form:
 * @code
 *   '#parents' => The location of field values in $form_state['values'],
 *   '#entity_type' => The name of the entity type,
 *   '#bundle' => The name of the bundle,
 *   // One sub-array per field appearing in the entity, keyed by field name.
 *   // The structure of the array differs slightly depending on whether the
 *   // widget is 'single-value' (provides the input for one field value,
 *   // most common case), and will therefore be repeated as many times as
 *   // needed, or 'multiple-values' (one single widget allows the input of
 *   // several values, e.g checkboxes, select box...).
 *   // The sub-array is nested into a $langcode key where $langcode has the
 *   // same value of the $langcode parameter above.
 *   // The '#language' key holds the same value of $langcode and it is used
 *   // to access the field sub-array when $langcode is unknown.
 *   'field_foo' => array(
 *     '#tree' => TRUE,
 *     '#field_name' => The name of the field,
 *     '#language' => $langcode,
 *     $langcode => array(
 *       '#field_name' => The name of the field,
 *       '#language' => $langcode,
 *       '#field_parents' => The 'parents' space for the field in the form,
 *          equal to the #parents property of the $form parameter received by
 *          field_attach_form(),
 *       '#required' => Whether or not the field is required,
 *       '#title' => The label of the field instance,
 *       '#description' => The description text for the field instance,
 *
 *       // Only for 'single' widgets:
 *       '#theme' => 'field_multiple_value_form',
 *       '#cardinality' => The field cardinality,
 *       // One sub-array per copy of the widget, keyed by delta.
 *       0 => array(
 *         '#entity_type' => The name of the entity type,
 *         '#bundle' => The name of the bundle,
 *         '#field_name' => The name of the field,
 *         '#field_parents' => The 'parents' space for the field in the form,
 *            equal to the #parents property of the $form parameter received by
 *            field_attach_form(),
 *         '#title' => The title to be displayed by the widget,
 *         '#default_value' => The field value for delta 0,
 *         '#required' => Whether the widget should be marked required,
 *         '#delta' => 0,
 *         '#columns' => The array of field columns,
 *         // The remaining elements in the sub-array depend on the widget.
 *         '#type' => The type of the widget,
 *         ...
 *       ),
 *       1 => array(
 *         ...
 *       ),
 *
 *       // Only for multiple widgets:
 *       '#entity_type' => The name of the entity type,
 *       '#bundle' => $instance['bundle'],
 *       '#columns'  => array_keys($field['columns']),
 *       // The remaining elements in the sub-array depend on the widget.
 *       '#type' => The type of the widget,
 *       ...
 *     ),
 *     ...
 *   ),
 * )
 * @endcode
 *
 * Additionally, some processing data is placed in $form_state, and can be
 * accessed by field_form_get_state() and field_form_set_state().
 *
 * @param $entity_type
 *   The type of $entity; e.g. 'node' or 'user'.
 * @param $entity
 *   The entity for which to load form elements, used to initialize
 *   default form values.
 * @param $form
 *   The form structure to fill in. This can be a full form structure, or a
 *   sub-element of a larger form. The #parents property can be set to control
 *   the location of submitted field values within $form_state['values']. If
 *   not specified, $form['#parents'] is set to an empty array, placing field
 *   values at the top-level of $form_state['values'].
 * @param $form_state
 *   An associative array containing the current state of the form.
 * @param $langcode
 *   The language the field values are going to be entered, if no language
 *   is provided the default site language will be used.
 *
 * @see field_form_get_state()
 * @see field_form_set_state()
 */
function field_attach_form($entity_type, $entity, &$form, &$form_state, $langcode = NULL) {
	// Set #parents to 'top-level' by default.
	$form += array('#parents' => array());

	// If no language is provided use the default site language.
	$options = array('language' => field_valid_language($langcode));
	$form += (array) _field_invoke_default('form', $entity_type, $entity, $form, $form_state, $options);

	// Add custom weight handling.
	list($id, $vid, $bundle) = entity_extract_ids($entity_type, $entity);
	$form['#pre_render'][] = '_field_extra_fields_pre_render';
	$form['#entity_type'] = $entity_type;
	$form['#bundle'] = $bundle;

	// Let other modules make changes to the form.
	// Avoid module_invoke_all() to let parameters be taken by reference.
	foreach (module_implements('field_attach_form') as $module) {
		$function = $module . '_field_attach_form';
		$function($entity_type, $entity, $form, $form_state, $langcode);
	}
}

/**
 * Loads fields for the current revisions of a group of entities.
 *
 * Loads all fields for each entity object in a group of a single entity type.
 * The loaded field values are added directly to the entity objects.
 *
 * field_attach_load() is automatically called by the default entity controller
 * class, and thus, in most cases, doesn't need to be explicitly called by the
 * entity type module.
 *
 * @param $entity_type
 *   The type of $entity; e.g., 'node' or 'user'.
 * @param $entities
 *   An array of entities for which to load fields, keyed by entity ID.
 *   Each entity needs to have its 'bundle', 'id' and (if applicable)
 *   'revision' keys filled in. The function adds the loaded field data
 *   directly in the entity objects of the $entities array.
 * @param $age
 *   FIELD_LOAD_CURRENT to load the most recent revision for all
 *   fields, or FIELD_LOAD_REVISION to load the version indicated by
 *   each entity. Defaults to FIELD_LOAD_CURRENT; use
 *   field_attach_load_revision() instead of passing FIELD_LOAD_REVISION.
 * @param $options
 *   An associative array of additional options, with the following keys:
 *   - 'field_id': The field ID that should be loaded, instead of
 *     loading all fields, for each entity. Note that returned entities
 *     may contain data for other fields, for example if they are read
 *     from a cache.
 *   - 'deleted': If TRUE, the function will operate on deleted fields
 *     as well as non-deleted fields. If unset or FALSE, only
 *     non-deleted fields are operated on.
 */
function field_attach_load($entity_type, $entities, $age = FIELD_LOAD_CURRENT, $options = array()) {
	$field_info = field_info_field_by_ids();
	$load_current = $age == FIELD_LOAD_CURRENT;

	// Merge default options.
	$default_options = array(
			'deleted' => FALSE,
	);
	$options += $default_options;

	$info = entity_get_info($entity_type);
	// Only the most current revision of non-deleted fields for cacheable entity
	// types can be cached.
	$cache_read = $load_current && $info['field cache'] && empty($options['deleted']);
	// In addition, do not write to the cache when loading a single field.
	$cache_write = $cache_read && !isset($options['field_id']);

	if (empty($entities)) {
		return;
	}

	// Assume all entities will need to be queried. Entities found in the cache
	// will be removed from the list.
	$queried_entities = $entities;

	// Fetch available entities from cache, if applicable.
	if ($cache_read) {
		// Build the list of cache entries to retrieve.
		$cids = array();
		foreach ($entities as $id => $entity) {
			$cids[] = "field:$entity_type:$id";
		}
		$cache = cache_get_multiple($cids, 'cache_field');
		// Put the cached field values back into the entities and remove them from
		// the list of entities to query.
		foreach ($entities as $id => $entity) {
			$cid = "field:$entity_type:$id";
			if (isset($cache[$cid])) {
				unset($queried_entities[$id]);
				foreach ($cache[$cid]->data as $field_name => $values) {
					$entity->$field_name = $values;
				}
			}
		}
	}

	// Fetch other entities from their storage location.
	if ($queried_entities) {
		// The invoke order is:
		// - hook_field_storage_pre_load()
		// - storage backend's hook_field_storage_load()
		// - field-type module's hook_field_load()
		// - hook_field_attach_load()

		// Invoke hook_field_storage_pre_load(): let any module load field
		// data before the storage engine, accumulating along the way.
		$skip_fields = array();
		foreach (module_implements('field_storage_pre_load') as $module) {
			$function = $module . '_field_storage_pre_load';
			$function($entity_type, $queried_entities, $age, $skip_fields, $options);
		}

		$instances = array();

		// Collect the storage backends used by the remaining fields in the entities.
		$storages = array();
		foreach ($queried_entities as $entity) {
			list($id, $vid, $bundle) = entity_extract_ids($entity_type, $entity);
			$instances = _field_invoke_get_instances($entity_type, $bundle, $options);

			foreach ($instances as $instance) {
				$field_name = $instance['field_name'];
				$field_id = $instance['field_id'];
				// Make sure all fields are present at least as empty arrays.
				if (!isset($queried_entities[$id]->{$field_name})) {
					$queried_entities[$id]->{$field_name} = array();
				}
				// Collect the storage backend if the field has not been loaded yet.
				if (!isset($skip_fields[$field_id])) {
					$field = $field_info[$field_id];
					$storages[$field['storage']['type']][$field_id][] = $load_current ? $id : $vid;
				}
			}
		}

		// Invoke hook_field_storage_load() on the relevant storage backends.
		foreach ($storages as $storage => $fields) {
			$storage_info = field_info_storage_types($storage);
			module_invoke($storage_info['module'], 'field_storage_load', $entity_type, $queried_entities, $age, $fields, $options);
		}

		// Invoke field-type module's hook_field_load().
		$null = NULL;
		_field_invoke_multiple('load', $entity_type, $queried_entities, $age, $null, $options);

		// Invoke hook_field_attach_load(): let other modules act on loading the
		// entitiy.
		module_invoke_all('field_attach_load', $entity_type, $queried_entities, $age, $options);

		// Build cache data.
		if ($cache_write) {
			foreach ($queried_entities as $id => $entity) {
				$data = array();
				list($id, $vid, $bundle) = entity_extract_ids($entity_type, $entity);
				$instances = field_info_instances($entity_type, $bundle);
				foreach ($instances as $instance) {
					$data[$instance['field_name']] = $queried_entities[$id]->{$instance['field_name']};
				}
				$cid = "field:$entity_type:$id";
				cache_set($cid, $data, 'cache_field');
			}
		}
	}
}

/**
 * Load all fields for previous versions of a group of entities.
 *
 * Loading different versions of the same entities is not supported, and should
 * be done by separate calls to the function.
 *
 * field_attach_load_revision() is automatically called by the default entity
 * controller class, and thus, in most cases, doesn't need to be explicitly
 * called by the entity type module.
 *
 * @param $entity_type
 *   The type of $entity; e.g. 'node' or 'user'.
 * @param $entities
 *   An array of entities for which to load fields, keyed by entity ID. Each
 *   entity needs to have its 'bundle', 'id' and (if applicable) 'revision'
 *   keys filled. The function adds the loaded field data directly in the
 *   entity objects of the $entities array.
 * @param $options
 *   An associative array of additional options. See field_attach_load() for
 *   details.
 */
function field_attach_load_revision($entity_type, $entities, $options = array()) {
	return field_attach_load($entity_type, $entities, FIELD_LOAD_REVISION, $options);
}

/**
 * Perform field validation against the field data in an entity.
 *
 * This function does not perform field widget validation on form
 * submissions. It is intended to be called during API save
 * operations. Use field_attach_form_validate() to validate form
 * submissions.
 *
 * @param $entity_type
 *   The type of $entity; e.g. 'node' or 'user'.
 * @param $entity
 *   The entity with fields to validate.
 * @throws FieldValidationException
 *   If validation errors are found, a FieldValidationException is thrown. The
 *   'errors' property contains the array of errors, keyed by field name,
 *   language and delta.
 */
function field_attach_validate($entity_type, $entity) {
	$errors = array();
	// Check generic, field-type-agnostic errors first.
	_field_invoke_default('validate', $entity_type, $entity, $errors);
	// Check field-type specific errors.
	_field_invoke('validate', $entity_type, $entity, $errors);

	// Let other modules validate the entity.
	// Avoid module_invoke_all() to let $errors be taken by reference.
	foreach (module_implements('field_attach_validate') as $module) {
		$function = $module . '_field_attach_validate';
		$function($entity_type, $entity, $errors);
	}

	if ($errors) {
		throw new FieldValidationException($errors);
	}
}

/**
 * Perform field validation against form-submitted field values.
 *
 * There are two levels of validation for fields in forms: widget
 * validation, and field validation.
 * - Widget validation steps are specific to a given widget's own form
 *   structure and UI metaphors. They are executed through FAPI's
 *   #element_validate property during normal form validation.
 * - Field validation steps are common to a given field type, independently of
 *   the specific widget being used in a given form. They are defined in the
 *   field type's implementation of hook_field_validate().
 *
 * This function performs field validation in the context of a form
 * submission. It converts field validation errors into form errors
 * on the correct form elements. Fieldable entity types should call
 * this function during their own form validation function.
 *
 * @param $entity_type
 *   The type of $entity; e.g. 'node' or 'user'.
 * @param $entity
 *   The entity being submitted. The 'bundle', 'id' and (if applicable)
 *   'revision' keys should be present. The actual field values will be read
 *   from $form_state['values'].
 * @param $form
 *   The form structure where field elements are attached to. This might be a
 *   full form structure, or a sub-element of a larger form.
 * @param $form_state
 *   An associative array containing the current state of the form.
 */
function field_attach_form_validate($entity_type, $entity, $form, &$form_state) {
	// Extract field values from submitted values.
	_field_invoke_default('extract_form_values', $entity_type, $entity, $form, $form_state);

	// Perform field_level validation.
	try {
		field_attach_validate($entity_type, $entity);
	}
	catch (FieldValidationException $e) {
		// Pass field-level validation errors back to widgets for accurate error
		// flagging.
		foreach ($e->errors as $field_name => $field_errors) {
			foreach ($field_errors as $langcode => $errors) {
				$field_state = field_form_get_state($form['#parents'], $field_name, $langcode, $form_state);
				$field_state['errors'] = $errors;
				field_form_set_state($form['#parents'], $field_name, $langcode, $form_state, $field_state);
			}
		}
		_field_invoke_default('form_errors', $entity_type, $entity, $form, $form_state);
	}
}

/**
 * Perform necessary operations on field data submitted by a form.
 *
 * Currently, this accounts for drag-and-drop reordering of
 * field values, and filtering of empty values.
 *
 * @param $entity_type
 *   The type of $entity; e.g. 'node' or 'user'.
 * @param $entity
 *   The entity being submitted. The 'bundle', 'id' and (if applicable)
 *   'revision' keys should be present. The actual field values will be read
 *   from $form_state['values'].
 * @param $form
 *   The form structure where field elements are attached to. This might be a
 *   full form structure, or a sub-element of a larger form.
 * @param $form_state
 *   An associative array containing the current state of the form.
 */
function field_attach_submit($entity_type, $entity, $form, &$form_state) {
	// Extract field values from submitted values.
	_field_invoke_default('extract_form_values', $entity_type, $entity, $form, $form_state);

	_field_invoke_default('submit', $entity_type, $entity, $form, $form_state);

	// Let other modules act on submitting the entity.
	// Avoid module_invoke_all() to let $form_state be taken by reference.
	foreach (module_implements('field_attach_submit') as $module) {
		$function = $module . '_field_attach_submit';
		$function($entity_type, $entity, $form, $form_state);
	}
}

/**
 * Perform necessary operations just before fields data get saved.
 *
 * We take no specific action here, we just give other
 * modules the opportunity to act.
 *
 * @param $entity_type
 *   The type of $entity; e.g. 'node' or 'user'.
 * @param $entity
 *   The entity with fields to process.
 */
function field_attach_presave($entity_type, $entity) {
	_field_invoke('presave', $entity_type, $entity);

	// Let other modules act on presaving the entity.
	module_invoke_all('field_attach_presave', $entity_type, $entity);
}

/**
 * Save field data for a new entity.
 *
 * The passed-in entity must already contain its id and (if applicable)
 * revision id attributes.
 * Default values (if any) will be saved for fields not present in the
 * $entity.
 *
 * @param $entity_type
 *   The type of $entity; e.g. 'node' or 'user'.
 * @param $entity
 *   The entity with fields to save.
 * @return
 *   Default values (if any) will be added to the $entity parameter for fields
 *   it leaves unspecified.
 */
function field_attach_insert($entity_type, $entity) {
	_field_invoke_default('insert', $entity_type, $entity);
	_field_invoke('insert', $entity_type, $entity);

	list($id, $vid, $bundle) = entity_extract_ids($entity_type, $entity);

	// Let any module insert field data before the storage engine, accumulating
	// saved fields along the way.
	$skip_fields = array();
	foreach (module_implements('field_storage_pre_insert') as $module) {
		$function = $module . '_field_storage_pre_insert';
		$function($entity_type, $entity, $skip_fields);
	}

	// Collect the storage backends used by the remaining fields in the entities.
	$storages = array();
	foreach (field_info_instances($entity_type, $bundle) as $instance) {
		$field = field_info_field_by_id($instance['field_id']);
		$field_id = $field['id'];
		$field_name = $field['field_name'];
		if (!empty($entity->$field_name)) {
			// Collect the storage backend if the field has not been written yet.
			if (!isset($skip_fields[$field_id])) {
				$storages[$field['storage']['type']][$field_id] = $field_id;
			}
		}
	}

	// Field storage backends save any remaining unsaved fields.
	foreach ($storages as $storage => $fields) {
		$storage_info = field_info_storage_types($storage);
		module_invoke($storage_info['module'], 'field_storage_write', $entity_type, $entity, FIELD_STORAGE_INSERT, $fields);
	}

	// Let other modules act on inserting the entity.
	module_invoke_all('field_attach_insert', $entity_type, $entity);

	$entity_info = entity_get_info($entity_type);
}

/**
 * Save field data for an existing entity.
 *
 * @param $entity_type
 *   The type of $entity; e.g. 'node' or 'user'.
 * @param $entity
 *   The entity with fields to save.
 */
function field_attach_update($entity_type, $entity) {
	_field_invoke('update', $entity_type, $entity);

	list($id, $vid, $bundle) = entity_extract_ids($entity_type, $entity);

	// Let any module update field data before the storage engine, accumulating
	// saved fields along the way.
	$skip_fields = array();
	foreach (module_implements('field_storage_pre_update') as $module) {
		$function = $module . '_field_storage_pre_update';
		$function($entity_type, $entity, $skip_fields);
	}

	// Collect the storage backends used by the remaining fields in the entities.
	$storages = array();
	foreach (field_info_instances($entity_type, $bundle) as $instance) {
		$field = field_info_field_by_id($instance['field_id']);
		$field_id = $field['id'];
		$field_name = $field['field_name'];
		// Leave the field untouched if $entity comes with no $field_name property,
		// but empty the field if it comes as a NULL value or an empty array.
		// Function property_exists() is slower, so we catch the more frequent
		// cases where it's an empty array with the faster isset().
		if (isset($entity->$field_name) || property_exists($entity, $field_name)) {
			// Collect the storage backend if the field has not been written yet.
			if (!isset($skip_fields[$field_id])) {
				$storages[$field['storage']['type']][$field_id] = $field_id;
			}
		}
	}

	// Field storage backends save any remaining unsaved fields.
	foreach ($storages as $storage => $fields) {
		$storage_info = field_info_storage_types($storage);
		module_invoke($storage_info['module'], 'field_storage_write', $entity_type, $entity, FIELD_STORAGE_UPDATE, $fields);
	}

	// Let other modules act on updating the entity.
	module_invoke_all('field_attach_update', $entity_type, $entity);

	$entity_info = entity_get_info($entity_type);
	if ($entity_info['field cache']) {
		cache_clear_all("field:$entity_type:$id", 'cache_field');
	}
}

/**
 * Delete field data for an existing entity. This deletes all
 * revisions of field data for the entity.
 *
 * @param $entity_type
 *   The type of $entity; e.g. 'node' or 'user'.
 * @param $entity
 *   The entity whose field data to delete.
 */
function field_attach_delete($entity_type, $entity) {
	_field_invoke('delete', $entity_type, $entity);

	list($id, $vid, $bundle) = entity_extract_ids($entity_type, $entity);

	// Collect the storage backends used by the fields in the entities.
	$storages = array();
	foreach (field_info_instances($entity_type, $bundle) as $instance) {
		$field = field_info_field_by_id($instance['field_id']);
		$field_id = $field['id'];
		$storages[$field['storage']['type']][$field_id] = $field_id;
	}

	// Field storage backends delete their data.
	foreach ($storages as $storage => $fields) {
		$storage_info = field_info_storage_types($storage);
		module_invoke($storage_info['module'], 'field_storage_delete', $entity_type, $entity, $fields);
	}

	// Let other modules act on deleting the entity.
	module_invoke_all('field_attach_delete', $entity_type, $entity);

	$entity_info = entity_get_info($entity_type);
	if ($entity_info['field cache']) {
		cache_clear_all("field:$entity_type:$id", 'cache_field');
	}
}

/**
 * Delete field data for a single revision of an existing entity. The
 * passed entity must have a revision id attribute.
 *
 * @param $entity_type
 *   The type of $entity; e.g. 'node' or 'user'.
 * @param $entity
 *   The entity with fields to save.
 */
function field_attach_delete_revision($entity_type, $entity) {
	_field_invoke('delete_revision', $entity_type, $entity);

	list($id, $vid, $bundle) = entity_extract_ids($entity_type, $entity);

	// Collect the storage backends used by the fields in the entities.
	$storages = array();
	foreach (field_info_instances($entity_type, $bundle) as $instance) {
		$field = field_info_field_by_id($instance['field_id']);
		$field_id = $field['id'];
		$storages[$field['storage']['type']][$field_id] = $field_id;
	}

	// Field storage backends delete their data.
	foreach ($storages as $storage => $fields) {
		$storage_info = field_info_storage_types($storage);
		module_invoke($storage_info['module'], 'field_storage_delete_revision', $entity_type, $entity, $fields);
	}

	// Let other modules act on deleting the revision.
	module_invoke_all('field_attach_delete_revision', $entity_type, $entity);
}

/**
 * Prepare field data prior to display.
 *
 * This function lets field types and formatters load additional data
 * needed for display that is not automatically loaded during
 * field_attach_load(). It accepts an array of entities to allow query
 * optimisation when displaying lists of entities.
 *
 * field_attach_prepare_view() and field_attach_view() are two halves
 * of the same operation. It is safe to call
 * field_attach_prepare_view() multiple times on the same entity
 * before calling field_attach_view() on it, but calling any Field
 * API operation on an entity between passing that entity to these two
 * functions may yield incorrect results.
 *
 * @param $entity_type
 *   The type of $entities; e.g. 'node' or 'user'.
 * @param $entities
 *   An array of entities, keyed by entity id.
 * @param $view_mode
 *   View mode, e.g. 'full', 'teaser'...
 * @param $langcode
 *   (Optional) The language the field values are to be shown in. If no language
 *   is provided the current language is used.
 */
function field_attach_prepare_view($entity_type, $entities, $view_mode, $langcode = NULL) {
	$options = array('language' => array());

	// To ensure hooks are only run once per entity, only process items without
	// the _field_view_prepared flag.
	// @todo: resolve this more generally for both entity and field level hooks.
	$prepare = array();
	foreach ($entities as $id => $entity) {
		if (empty($entity->_field_view_prepared)) {
			// Add this entity to the items to be prepared.
			$prepare[$id] = $entity;

			// Determine the actual language to display for each field, given the
			// languages available in the field data.
			$options['language'][$id] = field_language($entity_type, $entity, NULL, $langcode);

			// Mark this item as prepared.
			$entity->_field_view_prepared = TRUE;
		}
	}

	$null = NULL;
	// First let the field types do their preparation.
	_field_invoke_multiple('prepare_view', $entity_type, $prepare, $null, $null, $options);
	// Then let the formatters do their own specific massaging.
	// field_default_prepare_view() takes care of dispatching to the correct
	// formatters according to the display settings for the view mode.
	_field_invoke_multiple_default('prepare_view', $entity_type, $prepare, $view_mode, $null, $options);
}

/**
 * Returns a renderable array for the fields on an entity.
 *
 * Each field is displayed according to the display options specified in the
 * $instance definition for the given $view_mode.
 *
 * field_attach_prepare_view() and field_attach_view() are two halves
 * of the same operation. It is safe to call
 * field_attach_prepare_view() multiple times on the same entity
 * before calling field_attach_view() on it, but calling any Field
 * API operation on an entity between passing that entity to these two
 * functions may yield incorrect results.
 *
 * Sample structure:
 * @code
 * array(
 *   'field_foo' => array(
 *     '#theme' => 'field',
 *     '#title' => the label of the field instance,
 *     '#label_display' => the label display mode,
 *     '#object' => the fieldable entity being displayed,
 *     '#entity_type' => the type of the entity being displayed,
 *     '#language' => the language of the field values being displayed,
 *     '#view_mode' => the view mode,
 *     '#field_name' => the name of the field,
 *     '#field_type' => the type of the field,
 *     '#formatter' => the name of the formatter,
 *     '#items' => the field values being displayed,
 *     // The element's children are the formatted values returned by
 *     // hook_field_formatter_view().
 *   ),
 * );
 * @endcode
 *
 * @param $entity_type
 *   The type of $entity; e.g. 'node' or 'user'.
 * @param $entity
 *   The entity with fields to render.
 * @param $view_mode
 *   View mode, e.g. 'full', 'teaser'...
 * @param $langcode
 *   The language the field values are to be shown in. If no language is
 *   provided the current language is used.
 * @return
 *   A renderable array for the field values.
 */
function field_attach_view($entity_type, $entity, $view_mode, $langcode = NULL) {
	// Determine the actual language to display for each field, given the
	// languages available in the field data.
	$display_language = field_language($entity_type, $entity, NULL, $langcode);
	$options = array('language' => $display_language);

	// Invoke field_default_view().
	$null = NULL;
	$output = _field_invoke_default('view', $entity_type, $entity, $view_mode, $null, $options);

	// Add custom weight handling.
	list($id, $vid, $bundle) = entity_extract_ids($entity_type, $entity);
	$output['#pre_render'][] = '_field_extra_fields_pre_render';
	$output['#entity_type'] = $entity_type;
	$output['#bundle'] = $bundle;

	// Let other modules alter the renderable array.
	$context = array(
			'entity_type' => $entity_type,
			'entity' => $entity,
			'view_mode' => $view_mode,
			'display' => $view_mode,
			'language' => $langcode,
	);
	drupal_alter('field_attach_view', $output, $context);

	// Reset the _field_view_prepared flag set in field_attach_prepare_view(),
	// in case the same entity is displayed with different settings later in
	// the request.
	unset($entity->_field_view_prepared);

	return $output;
}

/**
 * Populate the template variables with the field values available for rendering.
 *
 * The $variables array will be populated with all the field instance values
 * associated with the given entity type, keyed by field name; in case of
 * translatable fields the language currently chosen for display will be
 * selected.
 *
 * @param $entity_type
 *   The type of $entity; e.g. 'node' or 'user'.
 * @param $entity
 *   The entity with fields to render.
 * @param $element
 *   The structured array containing the values ready for rendering.
 * @param $variables
 *   The variables array is passed by reference and will be populated with field
 *   values.
 */
function field_attach_preprocess($entity_type, $entity, $element, &$variables) {
	list(, , $bundle) = entity_extract_ids($entity_type, $entity);

	foreach (field_info_instances($entity_type, $bundle) as $instance) {
		$field_name = $instance['field_name'];
		if (isset($element[$field_name]['#language'])) {
			$langcode = $element[$field_name]['#language'];
			$variables[$field_name] = isset($entity->{$field_name}[$langcode]) ? $entity->{$field_name}[$langcode] : NULL;
		}
	}

	// Let other modules make changes to the $variables array.
	$context = array(
			'entity_type' => $entity_type,
			'entity' => $entity,
			'element' => $element,
	);
	drupal_alter('field_attach_preprocess', $variables, $context);
}

/**
 * Prepares an entity for translation.
 *
 * This function is used to fill-in the form default values for Field API fields
 * while performing entity translation. By default it copies all the source
 * values in the given source language to the new entity and assigns them the
 * target language.
 *
 * This is used as part of the 'per entity' translation pattern, which is
 * implemented only for nodes by translation.module. Other entity types may be
 * supported through contributed modules.
 *
 * @param $entity_type
 *   The type of $entity; e.g. 'node' or 'user'.
 * @param $entity
 *   The entity to be prepared for translation.
 * @param $langcode
 *   The language the entity has to be translated in.
 * @param $source_entity
 *   The source entity holding the field values to be translated.
 * @param $source_langcode
 *   The source language from which translate.
 */
function field_attach_prepare_translation($entity_type, $entity, $langcode, $source_entity, $source_langcode) {
	$options = array('language' => $langcode);
	// Copy source field values into the entity to be prepared.
	_field_invoke_default('prepare_translation', $entity_type, $entity, $source_entity, $source_langcode, $options);
	// Let field types handle their own advanced translation pattern if needed.
	_field_invoke('prepare_translation', $entity_type, $entity, $source_entity, $source_langcode, $options);
	// Let other modules alter the entity translation.
	$context = array(
			'entity_type' => $entity_type,
			'langcode' => $langcode,
			'source_entity' => $source_entity,
			'source_langcode' => $source_langcode,
	);
	drupal_alter('field_attach_prepare_translation', $entity, $context);
}

/**
 * Notify field.module that a new bundle was created.
 *
 * The default SQL-based storage doesn't need to do anything about it, but
 * others might.
 *
 * @param $entity_type
 *   The entity type to which the bundle is bound.
 * @param $bundle
 *   The name of the newly created bundle.
 */
function field_attach_create_bundle($entity_type, $bundle) {
	// Clear the cache.
	field_cache_clear();

	// Let other modules act on creating the bundle.
	module_invoke_all('field_attach_create_bundle', $entity_type, $bundle);
}

/**
 * Notify field.module that a bundle was renamed.
 *
 * @param $entity_type
 *   The entity type to which the bundle is bound.
 * @param $bundle_old
 *   The previous name of the bundle.
 * @param $bundle_new
 *   The new name of the bundle.
 */
function field_attach_rename_bundle($entity_type, $bundle_old, $bundle_new) {
	db_update('field_config_instance')
	->fields(array('bundle' => $bundle_new))
	->condition('entity_type', $entity_type)
	->condition('bundle', $bundle_old)
	->execute();

	// Clear the cache.
	field_cache_clear();

	// Update bundle settings.
	$settings = variable_get('field_bundle_settings', array());
	if (isset($settings[$entity_type][$bundle_old])) {
		$settings[$entity_type][$bundle_new] = $settings[$entity_type][$bundle_old];
		unset($settings[$entity_type][$bundle_old]);
		variable_set('field_bundle_settings', $settings);
	}

	// Let other modules act on renaming the bundle.
	module_invoke_all('field_attach_rename_bundle', $entity_type, $bundle_old, $bundle_new);
}

/**
 * Notify field.module the a bundle was deleted.
 *
 * This deletes the data for the field instances as well as the field instances
 * themselves. This function actually just marks the data and field instances
 * and deleted, leaving the garbage collection for a separate process, because
 * it is not always possible to delete this much data in a single page request
 * (particularly since for some field types, the deletion is more than just a
 * simple DELETE query).
 *
 * @param $entity_type
 *   The entity type to which the bundle is bound.
 * @param $bundle
 *   The bundle to delete.
 */
function field_attach_delete_bundle($entity_type, $bundle) {
	// First, delete the instances themselves. field_read_instances() must be
	// used here since field_info_instances() does not return instances for
	// disabled entity types or bundles.
	$instances = field_read_instances(array('entity_type' => $entity_type, 'bundle' => $bundle), array('include_inactive' => 1));
	foreach ($instances as $instance) {
		field_delete_instance($instance);
	}

	// Clear the cache.
	field_cache_clear();

	// Clear bundle display settings.
	$settings = variable_get('field_bundle_settings', array());
	if (isset($settings[$entity_type][$bundle])) {
		unset($settings[$entity_type][$bundle]);
		variable_set('field_bundle_settings', $settings);
	}

	// Let other modules act on deleting the bundle.
	module_invoke_all('field_attach_delete_bundle', $entity_type, $bundle, $instances);
}


/**
 * @} End of "defgroup field_attach"
 */
